Salim Ahmed Hamdan, the first al-Qaida suspect to be tried at the Guantánamo Bay prison camp, today was sentenced to five and a half years in prison for supporting terrorism.

Because Hamdan has already served five years at Guantanamo, the 40-year-old Yemeni national will only have to complete a six-month sentence.

The judge in his case, US navy captain Keith Allred, told reporters at the prison camp that it is unclear what future Hamdan faces in six months but that he would likely be eligible for an administrative review of his status.

No matter what penalty Hamdan had received, he remains subject to possible indefinite detention by the US military.

The defendant admitted before his sentencing that he continued to serve as a driver for Osama bin Laden after realising that he was working for a terrorist organisation.

Hamdan told the six-person military jury at Guantanamo that he continued to work for bin Laden only to support his family and apologised to the victims of al-Qaida attacks. Pentagon prosecutors dismissed the gesture and asked for at least a 30-year sentence.

The location where Hamdan will serve his sentence has not been formally announced, although moving him to a site in the US would likely present significant political difficulties.

Hamdan's conviction brings the White House's fight to try terrorist suspects full circle. It was Hamdan whose challenge to the original Guantánamo tribunals prompted a 2006 US supreme court ruling that conspiracy – of which the defendant was accused but not convicted - is not a war crime.

Yet supporters of the tribunal process asserted that Hamdan's acquittal by the jury of six military officers immunised the Bush administration from criticism that Guantanamo defendants are deprived of basic legal rights.

The tribunal allowed hearsay and inflammatory evidence but Allred blocked the admission of some of Hamdan's statements extracted through coercion.

At one point near the conclusion of the 10-day trial, Allred admitted that he may have given unclear instructions to the jury on whether an "enemy combatant", as the Pentagon designated Hamdan, can murder a uniformed soldier without violating the laws of war.

Neither side moved for a mistrial based on Allred's instructions, despite the possibility that the murky definition could set a complicated precedent for future prosecutions at Guantánamo.

Defence lawyers did not dispute during the trial that Hamdan provided assistance to bin Laden's network. Rather, they argued that Hamdan was a low-level player in the al-Qaida network, not the indispensable aide he was depicted as by the prosecutors.

Khalid Sheikh Mohammed, the alleged mastermind of the 9/11 attacks who was recently arraigned at Guantánamo, weighed in on behalf of Hamdan. In written testimony, Mohammed dismissed Hamdan as a mere chauffeur "not fit to plan or execute".